This article is about a preliminary study on the preparation and properties of Au-SiO2 composite sol,based on the request of hollow-core fiber for ultraviolet laser transmission.Some influence rules of the silica sol are analysised by orthogonal experiments,then a advisable formula of silica sol is confirmed.By observing and comparing the difference between Au-SiO2 composite sol and silica sol with TEM test,some reasons are presented on the basis of colloid chemistry theory.An important basis for the preparation of Au-SiO2 composite film is established according to the study on Au-SiO2 composite sol.